Patent Document 1 describes a power amplifier for use in power amplification of RF signals. The power amplifier described in Patent Document 1 is provided with a plurality of sets of a first amplification unit and a second amplification unit, in which a Doherty combiner is provided in each set. Furthermore, the power amplifier described in Patent Document 1 is provided with a broadband combiner combining output signals of the Doherty combiners. In a first amplification unit, a plurality of amplification circuits operating in Class AB or Class B is provided in parallel and a combiner combining output signals of the amplification circuits is further provided. In a second amplification unit, a plurality of amplification circuits operating in Class C is provided in parallel and a combiner combining output signals of the amplification circuits is further provided. In the power amplifier described in Patent Document 1, each first amplification unit, each second amplification unit, each Doherty combiner, and the broadband combiner are stored in a different chassis and the Doherty combiner can be exchanged.
In the power amplifier described in Patent Document 1, the first amplification units and the second amplification units are arranged in the vertical direction as illustrated in FIG. 5 of Patent Document 1. In the Doherty combiner corresponding to the set of the first amplification unit and the second amplification unit, two input connectors into which RF signals are input are disposed in such a manner as to be arranged in the longitudinal direction. The first amplification unit and the second amplification unit each have one output connector. The output connector of the first amplification unit disposed on the upper side is connected to the input connector on the upper side in the Doherty combiner and the output connector of the second amplification unit disposed on the lower side is connected to the input connector on the lower side in the Doherty combiner.
Patent Document 2 describes a solidified shortwave band transmission system of several tens of kW class. The solidified shortwave band transmission system described in Patent Document 2 has a combining unit containing a plurality of pre-combiner and one post-combiner. Moreover, a plurality of power amplifiers which can be individually detached and attached is provided in each pre-combiner. Each pre-combiner combines outputs of the plurality of power amplifiers and the post-combiner combines outputs of the plurality of pre-combiners.
Patent Document 3 describes a configuration in which a plurality of amplification units is disposed between a distributor and a combiner. The amplification unit described in Patent Document 3 is one obtained by integrating a plurality (for example, 8) of individual selection amplifiers as one unit. When an individual selection amplifier is added, the individual selection amplifier is added in terms of amplification unit.
Patent Document 4 describes a power combining apparatus having a plurality of band pass filters having mutually different pass bands and one or two or more circulators. The power combining apparatus described in Patent Document 4 has a configuration in which a first band pass filter and a second band pass filter are connected with a first circulator and an n-th (n is natural number.) circulator and an n+2-th band pass filter are successively connected through with an n+1-th circulator.
A television broadcasting organization obtains approval of undertaking the broadcasting industry by transmitting television signals using the frequency band obtained by dividing the UHF (Ultra High Frequency) band (470 to 862 MHz) or the VHF (Very High Frequency) band (170 to 230 MHz) by a fixed bandwidth as the unit. For example, a broadcasting organization using the UHF band obtains approval of undertaking the broadcasting industry using the frequency band obtained by dividing the UHF band by a 8 MHz bandwidth as the unit. Depending on countries, the bandwidth dividing the UHF band is sometimes 6 MHz or 7 MHz.